This PDF file contains the front matter associated with SPIE Proceedings Volume 7090, including the Title Page, Copyright information, Table of Contents, Introduction (if any), and the Conference Committee listing.

Conventional tracking systems measure time-space-position data and collect imagery to quantify the flight dynamics of tracked targets. A major obstacle that severely impacts the accuracy of the target characterization is atmospheric turbulence induced distortion of the tracking laser beam and imagery degradations. Tracking occurs in a continuously changing atmosphere resulting in rapid variations in the tracking laser beam and distorted imagery. These atmospheric effects, combined with other degradation effects such as measurement system motion, defocus blur, and spatially varying noise, severely limit the viability and accuracy of many tracking and imagery-based analysis methods. In 2007, using a high speed sled test, the feasibility of quantifying flight dynamics with stereo laser tracking and multi-video imagery was demonstrated. The technique acquires stereo views (two or more) of a moving test article that has an applied random speckle (dot) pattern painted on the surface to provide unique tracking points. The stereo views are reconciled via coordinate transformations and correlation of the transformed images. The 2007 results demonstrated that dual laser tracker data can be used to update camera calibration data for stereo imaging to extend the image correlation approach to moving field of view applications such as missile tracking and missile performance characterization, e.g., attitude measurements. However, these results were predominantly qualitative in nature, focusing on the degree of correlation. This paper will present quantitative results from 2008 outdoor centrifuge tests and assess the digital image correlation accuracy for time varying attitude and position measurements.

Naval operations in the littoral have to deal with the threat of small sea-surface targets. These targets have a low radar cross-section and low velocity, which makes them hard to detect by radar in the presence of sea clutter. Search lidars can provide an alternative detection capability for small sea-surface targets at ranges up to 10 km (using commercially available parts). The lidar clutter is much smaller than the radar clutter due to the smoothness of the sea surface for optical wavelengths, thus almost all laser light is scattered away from the receiver. By using a high rep-rate laser the search time is limited in order to be useful in the operational context of coastal surveillance and naval surface surveillance. In the same scenario, a laser range profiler with a high bandwidth, fast laser receiver can be used to for identification of the various contacts. To this end, the experimental results have to be compared to a database with premeasured or pre-calculated range profiles of possible targets. The good match between experimental and simulated laser range profiles implies that such a database can be constructed from 3D-target models, thus simplifying the database creation.

Present-day naval operations take place in coastal environments as well as narrow straits all over the world. Coastal environments around the world are exhibiting a number of threats to naval forces. In particular a large number of asymmetric threats can be present in environments with cluttered backgrounds as well as rapidly varying atmospheric conditions. During trials executed in False Bay a large amount of target, background and atmosphere data was gathered that is of use in analysis of optical characteristics of targets and backgrounds. During the trials a variety of backgrounds were recorded. We have used these backgrounds to validate the TNO background model MIBS to incorporate also coastal backgrounds and sunlit sea backgrounds. In the paper we show results of the background analysis, for coastal bay backgrounds. In particular the detection of small targets by automatic system may be hampered by small surface structure variations at the surface and near the horizon. The data that we analyzed are sea surface structure, temporal behaviour, and spectral differences during different environmental conditions that occurred during the trials. This data is essential to feed detection algorithms, and performance models for the assessment of sensor performance in coastal environment.

An imaging enhancement technique capable of mitigating the effect of atmospheric turbulence on wide field-of-view images is presented. The method is based on the local information fusion from a set of short-exposure anisoplanatic images. Since anisoplanatism affects short-exposure images locally, the synthetic imaging algorithm uses local image quality information. Pre-processing of the source data and use of a composed image quality metric are considered. The synthetic imaging technique is tested on experimental data. The synthesized images show an improvement in image quality compared to the original set of images.

We describe bimorph piezoelectric fiber actuators, which enable tip and tilt control in fiber collimators, as well as their integration into a fiber-array based beam-projection system. A mechanism for alignment of individual fiber actuators within the array was developed. It provides six degrees of freedom and allows for high subaperture density. The alignment procedures for a seven-subaperture prototype system as well as first results from evaluation experiments are presented.

The robustness and recoverability of the high-power femtosecond laser pulse filament in the presence of atmospheric aerosol scattering layer was studied by means of computer simulation. The obtained patterns of fluence and electron density in a laser filament demonstrate that these parameters acquire a stochastic character inside the aerosol layer and recover on leaving it. Filament energy decreases with distance inside the layer because of the water particles scattering and after the layer because of the amplitude-phase perturbations induced by aerosol particles. The equivalence of nonlinear aerosol medium and linear damping medium with equal to disperse dissipations was investigated.

Optical turbulence research contributes to improved laser communications and adaptive optics systems. This paper presents experimental measurements of scintillation and focal spot displacement to obtain optical turbulence information along a near-horizontal 2.33 km free-space laser propagation path. Calculated values for optical turbulence intensity (C²_n) and Fried parameter (r₀) are compared to scintillometer-based measurements for several cases in winter and spring. Scintillation index estimates from recorded signal intensities were corrected to account for aperture averaging. Optical measurements provided better estimates for C²_n and r₀ when a more incoherent laser source was used during the second part of the experiment (λ= 808 nm) in comparison to a more coherent laser source (λ= 1064 nm) used for the first part. Apparently, an calculation criterion for this kind of laser signal analysis is that the propagating light beacon be partially incoherent and uniformly illuminated across the transmitting aperture. Similarly, estimates of C²_n and r₀ based on focal spot displacement analysis were improved using the more incoherent laser source, particularly in strong turbulence conditions.

AFIT/CDE developed the High Energy Laser End-to-End Operational Simulation (HELEEOS) model in part to quantify the performance variance created by the natural environment in possible HEL engagements. As such HELEEOS includes a fast-calculating, first principles, worldwide surface to 100 km, atmospheric propagation and characterization package. This package is also available as a stand-alone module called the Laser Environmental Effects Definition and Reference or LEEDR. LEEDR enables the creation of profiles of temperature, pressure, water vapor content, optical turbulence, atmospheric particulates and hydrometeors as they relate to line-by-line layer transmission, path and background radiance at wavelengths from the ultraviolet to radio frequencies. Physics-based cloud and precipitation characterizations are coupled with a probability of cloud free line of sight (CFLOS) algorithm for air-to-air, air-tosurface, and surface-to-air (or space) look angles. This paper compares HELEEOS/LEEDR propagation assessments to measurements documented in published literature. Primary comparisons are to atmospheric boundary layer extinction measurements made using lidar systems at ultraviolet to near-infrared wavelengths and Doppler weather radars at RF wavelengths. The specific environments as recorded for the field experiments or radar observations in the literature are recreated using the probabilistic climatological database within HELEEOS/LEEDR. Comparisons of modeled climatological optical turbulence (C²_n) values to recent near surface measurements of C²_n are included. Preliminary results indicate the HELEEOS and LEEDR characterizations are able to accurately produce the major features and magnitudes in vertical profiles of extinction and backscatter in the atmospheric boundary layer at the UV, visible, near- IR, and centimeter wavelengths studied. The comparisons additionally show the models capture important geographic, seasonal, and time-of-day variations that appear in the measurements.

We report results from field experiments that have compared laser propagation in the near infrared (NIR) and mid-wave infrared (MWIR) in a variety of atmospheric conditions. Single frequency laser sources at 1.565 μm and 3.603 μm were transmitted through a single common aperture telescope to ensure that each beam was affected by nearly identical turbulence. Tests were performed on a one-way, 1.26 km path over land and on a round-trip, 2 x 1.41 km path that was mostly over water using a broadband retro-reflector. It is expected from theory that scattering and turbulence should have relatively less effect at longer wavelength, however quantitative measurements in real world conditions are important because of the complexity and simplifying assumptions required in the theory. Although communication and laser radar systems that operate in the NIR at ~1.5 μm benefit from well-developed sources and detectors, it is expected that propagation in the MWIR can offer a significant advantage. The objective of this work was to quantify the relative propagation effects under realistic conditions.

In December 2006, a 17-day propagation field experiment was conducted on a near-sea-surface 7.07 kilometer path over the Pacific Ocean outside San Diego Bay. This test offered an opportunity to compare the results from incoherent optical instruments with propagated 1.064 micron laser radiation on the same path. The comparison includes both the turbulence effects on the beam, and the extinction of the beam by aerosol particles and molecules. We also comment on the optical configuration of the laser test which prevented accurate measurement of some of the important transmission and scintillation effects.

Atmospheric aerosol particles affect the Earth's radiative balance both in the cloud-free and the cloudy atmosphere. The direct effect of aerosols is related with scattering and absorption of solar radiation, and as a consequence, reduction of the amount of radiation reaching the surface. The best parameter that quantifies this effect is the aerosol extinction, which can be derived from vertical, as well as, horizontal measurements. The purpose of this paper is to compare the aerosol optical properties registered by two types of instruments. The first is a standard 5-wavelength hand-held sun photometer yielding the vertical column extinction, the second a 7-wavelength transmissometer developed at TNO. This multi-band transmissometer provides horizontal, path-integrated transmission data at 7 wavelengths within the visible/infra red spectral range. The data used in the comparison were collected during an experiment near Scripps Pier in La Jolla near San Diego, in November 2006.

Optical turbulence is an important characteristic for laser propagation in the atmosphere. The optical turbulence causes refractive index fluctuations in the air. The accumulative atmospheric refractive index fluctuations can incur deleterious effects to a laser beam propagating in the atmosphere by distorting its wavefront. Accurate characterization of turbulence in the atmosphere is important to many light propagation studies and related applications. Temperature fluctuations/turbulences in the atmosphere are highly correlated with the atmospheric optical turbulence. In many occasions, optical turbulences profiles in the atmosphere were obtained through the measurements of temperature turbulence and other other atmospheric quantities, for example, air humidity. Therefore determination of temperature fluctuations/turbulences parameter is helpful to the measurement of optical turbulence. Thermosonde was commonly seen in measurements of C²_T in the past. Here we show that a direct lidar system is able to fulfill the task of C²_T measurements. And compared to the thermosonde measurements the proposed lidar method has many advantages.

The absorption and scattering coefficients of atmospheric aerosols were continuously measured with a Photoacoustic Soot Spectrometer (PASS, DMT Inc. USA) at a suburb site of Nanjing, one of the regions experiencing rapid industrialization in China. The measurements were carried out during autumn and winter 2007. A preliminary analysis of the data shows that, the scattering coefficient, B_scat, is two to ten times larger than the absorption coefficient, Babs, implying that the aerosols formed/emitted in this area are more scattering than previous assumed, and can be more important in cooling the Earth-atmosphere system. The results also indicate that the absolute values of both parameters are very much dependent on the meteorological conditions, such as wind speed and direction, fog, rain, etc. as well as the time of the day. Higher values often appear at nighttimes when wind is weak, especially when a temperature inverse layer is present near the surface. Higher values of B_scat and B_abs were also observed under hazy and foggy weather conditions or when wind is blown from east, where a large industrial zone is located. Simultaneous measurements of the number concentrations, chemical compositions, and size distributions of aerosol particles are used to explain the characteristics of the changes in B_scat and B_abs.

The effect of cirrus cloud on radiative transfer depends on its microphysical properties. The water content and number concentrations of ice particles in tropical anvil cirrus measured during the ACTIVE (Aerosol and Chemical Transport in Tropical Convection) field campaign (from November 2005 to February 2006 in Darwin area, Australia) are analyzed. Some advanced particle probes are utilized during this campaign, including Cloud Imaging Probe (CIP) and Cloud Particle Imager (CPI). A statistical analysis of the fifteen cases (only the slow phase of anvil cirrus with the height ranging from 9.7 to 14.9 km and temperature ranging from -70.4°C to -30.0°C, are considered) shows that the typical value of ice water content (IWC) is 10^-2 g m^-3, and the number concentrations of ice particles measured by CIP (>100μm) and CPI (>5μm), are 10¹ and 10² L^-1, respectively. The changes in median of IWC in anvil cirri with temperature (or altitude) are examined and compared among different phases of Australian monsoon.